1. Field of the Invention
The present invention relates to a machine for simultaneously caulking a periphery of both axial end surfaces (hereinafter referred to as both-end-caulking machine) of an object.
2. Description of the Related Art
The basic construction and mechanism of the both-end-caulking is known from Japanese Patent Application Laid-Open No.11-188435. However, the both-end-caulking machine has a pair of left and right ball threads (hereinafter simply referred to as left and right ball threads) and its constituent features are unknown.
In the both-end-caulking machine disclosed in Japanese Patent Application Laid-Open No. 11-188435, a lower caulking punch is stationary, whereas an upper caulking punch is moved downward to caulk both axial ends of a shaft. However, because the lower caulking punch is stationary, the shaft moves downward by a caulking amount required to caulk the lower axial end of the shaft at a caulking time and becomes eccentric. In a case where the upward and downward movement of the caulking punch is controlled by using an actuator, such as a hydraulic cylinder, it is difficult to finely adjust a caulking load and the caulking amount. Hence, it cannot be said that the both-end-caulking machine has a high processing precision. Another problem of the both-end-caulking machine is that the use of the hydraulic cylinder causes the both-end-caulking machine to be large and thus a wide installing space is required.
The present invention has been made in view of the above-described situation. Accordingly, it is an object of the present invention to provide a both-end-caulking machine capable of solving the above-described problems and accomplishing a caulking process efficiently.
To achieve the object, the present inventors have made an energetic investigation and found that the problems of the conventional art can be solved by a machine for simultaneously caulking both axial ends of an object, in which an upper pressure plate having a first caulking punch mounted thereon is screwed to one side of left and right ball threads, and a lower pressure plate having a second caulking punch mounted thereon is screwed to the other side of the left and right ball threads, in such a way that the upper pressure plate and the lower pressure plate are moved relative to each other in a direction parallel to a caulking direction. In this regard, please refer to FIG. 5.
The present inventors have also found that fine adjustment of a caulking load and a caulking amount can be accomplished by using a servo motor which electrically controls an operation of moving the upper pressure plate and the lower pressure plate relative to each other. It is possible to make the caulking machine compact by utilizing the servo motor in operating the caulking machine.
The present inventors have made further study and examination, and completed the present invention.
Accordingly, the present invention relates to the following.
(1) A machine for simultaneously caulking both axial ends of an object, in which an upper pressure plate having a first caulking punch mounted thereon is screwed to one side of left and right ball threads, and a lower pressure plate having a second caulking punch mounted thereon is screwed to the other side of the left and right ball threads, in such a way that the upper pressure plate and the lower pressure plate are moved relative to each other in a direction parallel to a caulking direction such that the object is caulked.
(2) A machine according to above (1), wherein the left and right ball threads have the same pitch.
(3) A machine according to above (1) or (2), wherein the number of the left and right ball threads provided for one caulking machine is two.
(4) A machine according to any one of above (1) through (3), wherein a servo motor electrically controls an operation of moving the upper pressure plate and the lower pressure plate relative to each other.
(5) A machine according to any one of above (1) through (4), wherein whether a periphery of both axial end surfaces of the object has been normally caulked is automatically determined based on a caulking load and a caulking amount obtained at a caulking time.